Will Cycles eventually replace Blender Internal?
Update (5 years later)

Yes, for the upcoming Blender 2.8 release, Blender Internal has finally been superseded by Cycles. 





As far as I know, It is not yet officially confirmed. I asked a developer on IRC and he said No. However, one of the other developers has this on his blog.


  The goal of Cycles is to probably replace the Internal Render Engine
  in 1-2 years and have a fast and modern Render/Shading system which
  can be used for production rendering and for animation as well.


from code.blender.. the main developer also hints with..


  There may of course be developers that want to continue developing
  Blender Internal, and the intention is not to drop it immediately.


From BlenderGuru


  Cycles will eventually replace the internal rendering engine, becoming
  the standard that every Blender user will soon use. The sooner you can
  jump aboard, the better.


It seems such a decision was made a long time ago too.


  @andrewpprice There has been no further development for the BI (for
  about 2 years now) apart from critical crash fixes. That won't change.


It also seems that there is an ongoing project that is extending the Internal Renderer

It is all inconsistent information here and there but all very credible sources, so a definitive answer for this would be, It has not yet been confirmed.